Olefinic polymers such as polyethylene, polypropylene, polyvinyl chloride, polystyrene and polyesters are subject to photo-oxidation when exposed to sunlight over extended periods of time. This photo-oxidation initiates deterioration of the polymer by breaking the polymer chain and by causing formation of carbonyl groups in the molecule. As the oxidation continues, the polyolefin cracks or crazes and loses tensile strength to the point of mechanical failure. A number of ultraviolet inhibitors have been proposed which inhibit photo-degradation of many polymers, resins and polyesters. However, some of the most effective of these known ultraviolet inhibitors, such as lower alkyl hydroxyphenyl benzotriazoles, are not compatible with such polyolefins as polyethylene, polypropylene and polystyrene and polymers which contain high molecular weight hydrocarbon chains due to exudation from the polymer soon after being incorporated therein.
Also it has been found that many effective stabilizers for halogen containing polymers such as polyvinyl chloride, polyvinylidene chloride and the like are not effective stabilizers for hydrocarbon polyolefins, since stabilizers for such halogen-containing polymers function essentially as halide scavengers, thus serving no purpose in the hydrocarbon olefinic polymers and which, in some cases, actually alter desirable properties of the hydrocarbon polymer. Similarly, certain stabilizers which are emminently suitable as UV inhibitors in such cellulose ester polymers as cellulose triacetate and cellulose acetate butyrate are not sufficiently effective for hydrocarbon polymers.
Although certain benzotriazole stabilizers have been recently proposed in U.S. Pat. Nos. 3,230,194 and 3,253,921, these benzotriazoles are normally solid substances which are mixed with the polymer to provide protection but which are not retained over long duration in the polymeric material and, therefore, do not provide lasting protection against UV light absorption in these polymeric products. It is believed that these benzotriazoles in their normally solid state do not penetrate the internal polymeric structure for lasting incorporation therein. Similar difficulties are encountered with triazoles containing polar substituents such as SO.sub.2 NH.sub.2, amine derivatives thereof, SO.sub.3 Na, COONa, etc. Additionally, in the case of the lower alkyl benzotriazoles, the lower alkyl substituents are known to be incompatible with high molecular weight hydrocarbon type polymers, as is the case with stabilizers proposed in U.S. Pat. No. 3,018,269. In other cases, crowding of the alkyl substituent vicinal to the --OH group on the phenol ring produced a hindered phenol moiety which alters the UV absorption range, so that compounds such as 2-(3'-alkyl-2' -hydroxyphenyl)benzotriazoles and the 2-hydroxyphenyl naphthotriazoles are not sufficiently sensitive to effectively prevent deterioration due to UV light radiations within the critical 2,900A to 3,700A band range which most often causes the degradation of the polymer through discoloration and crazing.
Polyacrylamides, polyamides, polyacrylates and polycarbonates are also affected by UV light exposure such that they tend to discolor and darken; further, certain dyed fibres of these polymers have a tendency to fade under prolonged exposure to daylight. Accordingly, avoidance of these problems by economical incorporation of a suitable stabilizer is highly desirable.
In the case of non-polymeric materials, it is known that certain dyes and pigments are not resistant to the effects of sunlight and fade when exposed to ultraviolet radiation within the range of 250-400mu. Many transparent materials useful in sheets or films, in addition to developing undesirable color resulting in the reduction of transparency, also become brittle, lose their elasticity, crack and eventually completely deteriorate. Paints, varnishes, lacquers, and the like are particularly prone to these effects, and in connection with these latter materials, the transparency factor is of paramount concern. Thus, it is of prime importance that any stabilizer employed for these purposes be colorless and chemically inert so as to avoid coloration or formation of colored impurities.
In the case of hair dyes and sunscreening lotions, UV light stabilizers comprise an essential ingredient in the formulation to protect against harmful color changes or burning caused by sunlight. However, many of the stabilizers employed do not provide adequate protection over the entire range of harmful sun rays and are not complete sun screening agents. Thus, the development of a cosmetic cream, hair dye or sunscreening lotion containing a stabilizer having screening properties over the entire range of 2500A to 3800A is highly desirable.
It is therefore an object of this invention to provide a product of manufacture incorporating an ultraviolet absorbent and heat stabilization material of the benzotriazole type capable of conferring a high degree of long lasting stability to the olefinic and other polymers and non-polymeric materials, which stabilizer is substantially colorless and which is capable of intimate and uniform penetration into the internal polymeric structure or molecular arrangement and formulations of non-polymeric materials.
Another object of this invention is to provide a sunscreening or hair dyeing product which is completely stabilized against ultraviolet radiations within the range of 250 to 400 mu.
It is another object of this invention to provide a method for preparing such an improved stabilized polymer, paint, varnish, dye and sunscreening lotion.
It is a further object of this invention to provide a novel polymeric substance containing a completely compatible and intimately distributed stabilizer having sustained resistance to deterioration.
It is also an object of this invention to provide a complete sun screening formulation.
It is still another object to provide novel product formulations of extended life and having stabilized properties over a long duration, which formulations comprise polymeric materials, including halogen, oxygen and nitrogen containing polymers and paints, dyes, varnishes and cosmetics, including face creams and sunscreening lotions.
Still another object is to provide a stabilized polymer which possesses extended resistance to crazing, cracking or discoloration and which is suitable for use with fibres in the manufacture of dyed fabrics.
These and other objects of the present invention will become apparent from the following description and disclosure.